BUILD Blog


Rainscreens

Despite the growing popularity of rainscreen systems, we find that most people don’t know much about them and don’t understand why they are important to architecture. Like most innovative building systems it was the Europeans that first introduced the concept. One of the first examples we remember seeing is the IRCAM music school completed in Paris in the late 70’s by Renzo Piano. In the last decade we’ve noticed a growing interest and use of raincreens on buildings and houses here in the northwest. The concept of a rainscreen is to create an air gap between the siding material and the water-proof surface. This allows the structure to breathe a bit. Current building codes require structures to be sealed up so tightly that it’s causing unforeseen problems. More traditional siding systems often trap moisture between the various layers of materials. Differences in air pressure between the outside and inside of a building can actually drive air and, more dangerously, water into the building. The rainscreen system uses a water proof membrane to keep the water out, but it allows a bit of air movement – it’s like a Gore-tex wrap for your building or house. This membrane is a softer, more delicate material, it’s also sensitive to sunlight; UV rays will eventually break down the product if directly exposed. This is where the siding comes in. The siding, or skin of the building, is required for protection from physical harm like soccer balls and also to shield the membrane from sunlight. There is typically an air gap between the skin and the membrane of approximately one inch. If detailed and constructed correctly the system allows the building to breathe, allows the inside and outside air pressure to balance better and allows a tremendous variety of materials to be used as the skin. It is a more expensive system and requires more time and care for the installation but a well made rainscreen is hot, modern and functional.

Rainscreen Diagram by BUILD llc

1. Panel: Panel thicknesses vary; we’ve found most of them to be 5/16” thick. Panel sizes are typically 4’ x 8’ and 4’ x 10’. Products that we’ve had success with so far are Cembonit by CBF, Hardie-Panel, Swiss Pearl, Fincolorply, and Cor-ten steel.
2. Fastener: Typically we use a #8 wood screw with a gasketed hex head. Some panel types require specific fasteners. It’s also possible to flush mount flat head screws if the panels are properly pre-drilled, and if you have a lot of free-time. The fastener geometry is typically 12 to 24 inches on center in each direction. It’s very important to line the fasteners up on a grid as the fastener pattern becomes part of the finished look of the rainscreen system.
3. Vertical Runners: Trex is a great product for this application because it doesn’t move axially and it doesn’t rot. The dimensions of the runners entirely depend on the specifications required of the panel product – we tend to use 3/4” x 3/4” strips more often than anything else. Cedar or pressure treated lumber can also be used, be cautious of the expansion and contraction of these products.
4. Air Space: The dimension of air space typically ranges between ¾” to 1-1/2” depending on the panel product specifications
5. Membrane: This membrane is basically like Gore-tex for your house – it keeps the water out but lets air through (it lets your house breathe). There are many different brands, we like VaproShield because of the products function, durability and that they just started making it in black so that the membrane disappears in the shadows.
6. Flashing: The flashing we use at window wraps (like the one above) is typically a peel & stick application. It is flexible to deal with all sorts of different situations and angles.
7. Sheathing: You can either use ½” plywood and install flat blocking at all of the panel joints or use ¾” plywood behind all panels – we recommend the ¾” as it is MUCH less work. In either case you’ll want to use CDX plywood – don’t use that OSB crap here.
8. Framing: Typically 2×6 framing at exterior walls but this could vary depending on the situation.
9. Reveal: Typically ¼” but this varies with the panel product and desired finish look.

Okay, let’s get to some examples around the Seattle area:

Seattle Orthopedic Center at 2409 N 45th St
The project seems to use the Fincolorply system, or something very close to it. A very well crafted building that we recommend checking out. It displays two-different panel types.
Architect: Collins Woerman

Seattle Orthopedic Center

Seattle Orthopedic Center
[Photos by BUILD llc]

The William H. Foege Building at NE Pacific Str & 15th Ave NE
The panels seem to be a fired clay, almost brick-like in look and texture. The building is a very impressive display of the rainscreen system
Architect: Anshen + Allen

William H. Foege Building

William H. Foege Building

William H. Foege Building
[Photos by BUILD llc]

Medina Residence near Seattle
The residence uses the Swiss Pearl system and is designed with the precision of a cabinet at the exterior.  The panel system continues inside to certain areas of the interior.
Architect: BUILD llc

Medina residence

Medina residence

Medina residence
[Photos by Swiss Pearl]

Camano Cabin on Camano Island
The residence uses steel cor-ten panels as its rainscreen. The panels develop a layer of rust which continues to weather over time but protects the inner layers of the panel.
Architect: BUILD llc

Camano Cabin

Camano Cabin

Camano Cabin
[Photos by BUILD llc]

Dr. Marc Ferrin Residence on Bainbridge Island
The residence has just been wrapped with the membrane and will soon be receiving a skin of Cembonit rainscreen.
Architect: BUILD llc

Dr. Marc Ferrin Residence

Dr. Marc Ferrin Residence
[Photos by BUILD llc]

It’s taken us several years and many jobs to gather the resources and knowledge about these rainscreen systems. So why do we take the time & effort to post this info online for anyone to use and distribute for free? Because the battle against ugly, senseless architecture is a tough one and we need all the help we can get. Cheers

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38 Comments so far
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[…] all about them in this great post at BUILD LLC’s blog: It’s taken us several years and many jobs to gather the resources and knowledge about these […]

Pingback by rainscreens, explained at materialicious

Thanks for sharing! As you note, rainscreens have been around for a long time, and I remember learning about the rainscreen principle way back in school. The way it was explained back then was that the screen itself was intended to shed water mechanically while still allowing air circulation and pressure equalization in the cavity (kind of like installing lap siding over furring strips, with screened air inlets at the top & bottom). With that in mind, I tend to think of applications with gapped panels, which allow for some rain penetration, as “open rainscreens”. Any thoughts on issues with UV resistance of the weather barrier membrane, and for that matter, insects taking up residence in the cavity behind the panels?
Nice work!

Comment by Markus Kolb

Markus – good points. Indeed, the term “open rainscreen” is applicable to the types of systems in this post. Technically a “closed” system could also function just fine – similar to the lap siding over furring strips you mention.

While the rainscreen should shed most of the water mechanically the water proof barrier still needs to be designed as if it is the only defense against water – especially with these waterfront homes in the northwest.

The bug issue is always something we worry about but haven’t had problems with so far. We suspect that there is something in the membrane that bugs don’t like. Introducing a bug repellent membrane would be a very marketable addition for VaproShield though. On one of our projects a mesh bug-screen was installed behind the panels – this will do a great job at keeping everything out of the air gap; it generates its own set of challenges and weathering issues though.

We haven’t had any problems with the UV resistance once the skin is on – so long as the skin is detailed and built correctly with reveals of 1/4″ or smaller the constantly changing angle of the sun (when it’s out here in the northwest) doesn’t expose any of the membrane long enough to break down the material. However during construction, it’s always challenging to get the skin on quickly enough so that the fully exposed membrane doesn’t get too much sunlight. The products continue to improve and we suspect that eventually the membrane itself will be UV resistant.

Comment by buildllc

Terrific post!

One thing that we’ve recognized about rainscreen systems is that they are very similar in principle to masonry veneer systems that have been around for many years – exposed masonry with air gap separating it from the membrane. This just makes sense. Yes, thanks for sharing.

Comment by Bret

[…] a must read article for anyone not familiar with this wonderful architectural detail/design: the rainscreen. peace. […]

Pingback by Linkage - Rainscreen Systems - blueverticalstudio

Fascinating, and very useful. I’m curious about how well these systems work in harsher climates – for example, in conditions of ice, snow, or blowing snow.

Comment by Sarah

Thanks for the comments all- glad you enjoyed the summary. As for your comment Sarah- you raise an excellent point- we had one panel crack on a screen system where the fastener hole didn’t allow for the differential movement between the runner and the panel. Larger variations in temperature, humidity, etc. will only exacerbate this issue. Following the recommendations of product manufacturers (which will invariably rule out some products based on specific climates) is always a good initial design step.

Comment by buildllc

I just want to say I really like your blog. It’s so refreshing to know there are people out there that are concerned with the greater good. It would have been easy for you guys to talk about self centered hype and have your blog function as a promotion for your studio, but you choose not to.

Keep up the fabulous work!

-jay

Comment by jay dokken

Hey Guys,

Incredible post! Thanks for sharing the screen-luv.

I put a quick post on my blog: http://www.shawnbusse.com/private/houseblog/rainscreen-design

One quick question: Why CDX and not OSB for sheathing? I’m not partial to one or the other, but I see lots of OSB in use in Portland…

Comment by shawnbusse

Shawn – CDX is a stronger product and you can also get it in marine grades. Since the rainscreen is essentially “hanging” off the sheathing, something with more integrity in more directions is required. Oriented Strand Board comes apart more easily and doesn’t deal well with water. It has a confusing name – there’s nothing oriented about the product, the wood wafers are glued up in entirely random patterns.

Comment by buildllc

Thanks guys – that’s great info!

Comment by shawnbusse

Thanks for info and sharing. Greatly appreciated.

What type of fasteners did you use with the corten panels on the Camano Island project? Are they a black anodized fastener? Also, could you post an image or detail of the mesh bug screen assembly?

Comment by Chris

Chris-
We used a black #1 flathead self-tapping screw made out of a material that currently escapes our memory. It is a common fastener through companies like Fastenal, McMaster Carr and our very own Tacoma Screw. I believe you can find it by using that limited spec I gave you and requesting the type that is corrosion resistant…
The mesh is used on the vertical seams of the panels. We recommend a tight metal screen (yellow jackets can’t eat through it) fastened to the vertical runners on either side of the vertical gap. For the horizontal seams, a small drip flashing can be used that fills the gap and laps (a tiny bit) over the panel below. For doors/ windows, the last runner can be placed (very nearly) against the window/ door frame to close the gap.
Frankly, we have not experienced problems with ‘open screens’ and pests; and the amount of gymnastics required to pest-proof (and perhaps trap pests in?!) is problematic and fussy. Not to promise against pests, but we haven’t experienced those ourselves….

Comment by buildllc

nice post. for some reason, i find a lot of architects know nothing about rainscreens – confounding. it’s used a lot overseas, esp. in DE, CH and AT. i’ve got a few photos of an extreme ventilated rainscreen in basel.

the collins woermann project (on 45th) does look like prodema/parklex. basically parklex and prodema are offshoots of same product both pricey, one is less expensive than the other (i think prodema). it looks a little artificial, but not as orange as OSKA’s sw branch library.

CO architect’s foege bldg is a terracotta rainscreen – not shildan($$$) but still a nice product – maybe terreal terracotta? i really like the thinner “baguette” as sunscreens.

of course your work speaks for itself. how has the medina’s swisspearl weathered? and the corten? after a rick joy lecture about the nomad house (corten huts), there was a really ‘heated’ debate about using metal in the desert – but pulling it off the building is an effective way of keeping it cooler.

the exposed fasteners are always a bonus. additionally, you must specify the ‘swiss norm’ – all slots or hex’s must be oriented in the same direction…

another benefit to ventilated rainscreens is the “chimney effect” – increased cooling in summer and the same space further insulates in winter – thus making it ideal in temperate climates. the increased ventilation reduces mold/mildew build up (highly beneficial here in NW)

some other products:
minerit
eternit/swisspearl
slatescape
plywood – cheap and effective, a la h&dem’s plywood house & studio frei near vitra
trespa
terraclad

metal systems (rheinzink, copper) are equally nice

Comment by mike

Mike – we’d love to see that rainscreen in Basel. The Medina residence is just wrapping up so we haven’t had a chance to see how the Swiss Pearl weathers yet. The corten weathers quite nicely here in the northwest with all of the salty sea air. Sometimes we’ll spray down the panels with salt water prior to installation to jump start the weathering process. Thanks for the list of products – several materials on there that we weren’t familiar with.
-Andrew

Comment by buildllc

[…] Posts Re-thinking Construction DocumentsSimple, modern furnitureRainscreensThe Work of Mathias Klotz in ChileSCULPTURE PARKSMid-century modernizationSun Screens […]

Pingback by Cor-ten Architectural Siding « BUILD Blog

The comments about rainscreens in Europe are right-on, particularly as far as commercial projects are concerned (makes our cardboard houses with little wood furring strips and hardipanel seem pretty chincy). One thing that’s really interesting about many European implementations is the integration of an exterior insulation system, with extremely little thermal bridging, without any of the pitfalls of the EIF systems we tend to use Stateside. Check out the Erofox system, for example.

Comment by Markus Kolb

Great post. I am planning on using this system here in New England on a bank addition. Currently the building is a traditional modular two story structure with vinyl siding. To make it more commercial and modern looking, I was going to clad the addition in Cembonit panels, with some type of accent trim. Questions;

In your detailed images, I note that there are no EPT rubber underlaying strips. Is the detail a Cembonit application?

What would you suggest for trim (color matching is important) and would you make the trim part of the rainscreen or surface mount it, like a batten, on top of the Cembonit?

Thanks for any help.

Comment by Jon Wyman

Jon – The EPT rubber underlay is a component we’re just starting to use on rainscreens. It wasn’t a requirement with the Cembonite systems in the past but the mfr has included the rubber strips on the last couple of jobs – so we have incorporated it into the detailing. The rubber strips allow a bit more flexibility between the rigid panel and the vertical runners which are not always uniform. The EPT should really be in our detail as it is becoming more typical.
Trim is a tough one… being modernists and minimalists we’re usually looking for solutions to eliminate trim. A well designed rainscreen is very satisfying as a field of flush panels with crisp shadow reveals. In our own vocabulary I’d look to incorporate a “trim” in with the rainscreen system – flush with the panels but adding a geometry which breaks from the panels. It would be a shame to go to all the work of a rainscreen system and cover up the reveals with a trim or batten. Just our two cents…

Comment by buildllc

Thanks for the info. As for your response about modernism and trim; I agree, but considering that I am trying to introduce the modern into a traditional building,I am detailing the rainscreen panels at varying thicknesses to ‘add a geometry that breaks from the panels’.

Comment by Jon Wyman

We’re very interested in cladding our addition in Swiss Pearl. What are approximate costs for the material and shipping?

Comment by Barbara Thompson

This is great! Thanks for all the info. It’s exactly what I was looking for. I’m designing my own house in Athens, GA, and I’ve been investigating rainscreens as a way to use reclaimed unmilled lumber. I’m also interested in cor-ten. Did you over-size the screw holes and cover with neoprene in order to avoid oil-canning? I’m trying to figure out all the necessary detailing…..I’m also a little worried about rust colored run-off onto adjacent surfaces.
Thanks again!

Comment by Lori Bork

one more question about the cor-ten… Do you mind posting your supplier? I understand that U.S. Steel, who came up with the proprietary name, no longer manufactures it. I’ve found one alternative at weatheringsteel.com, but they don’t seem to have many built examples they can show me.

Comment by Lori Bork

Barbara – The Swiss Pearl product was in the $7 per square foot range when we last used it a couple of years ago (not including shipping, machining or install). With shipping costs dramatically on the rise I would check with your local/regional supplier for these costs. The Swiss Pearl product is also very specific in terms of how it is machined and installed, subsequently adding to the costs. More so than similar products, you’ll want to carefully review the Swiss Pearl specifications and methods.

Comment by buildllc

Lori – the supplier is: Corrugated Metals Inc. out of Chicago: http://www.corrugated-metals.com
We wanted flush mounted flat head screws in the cor-ten rainscreen, so we used a thicker cor-ten panel (~1/8″) and countersunk the fasteners. Oversizing the holes for expansion and contraction seems like a good detailing idea if the fasteners are to sit proud though. The cor-ten will most certainly discolor whatever is underneath.

Comment by buildllc

Thank you! Your blog is beyond helpful. As a homeowner designing/building our own home, there is so little information out there about options beyond James Hardie. Hopefully more people will take an interest in design and architecture and adapt more european and alternative building techniques and materials!

Comment by Barbara Thompson

I notice in your intro you mention Hardi-Panel as a rainscreen material. I am also finding it more difficult to get Cembonit panels in my area and the Swiss Pearl panels prove too costly. Can I really use Hardi-Panel in this application as you have detailed? Everything I find on the manufacturer’s website tells me that it is to be applied directly to sheathing. Thanks again.

Comment by Jon Wyman

Jon – you’ll want to check with Hardi on their warranty and whether or not using the material as a rainscreen voids their coverage, but we’ve seen it used as a true rainscreen around town. We’re noticing that with rainscreen systems becoming more common manufacturers are fine-tuning their installation techniques and sometimes modifying the warranty on the product (based on how its installed). If you’re in Seattle go check out Nicholas Court at 1413 15th Ave. If you’re not in the area here is a link to some photos of the project: http://www.urbanfundinc.com/nicholas.htm

Comment by Andrew

This is great discussion on rain screens. Check out this website I found. New product! It works with Vinyl siding, wood siding and Fiber cement siding

http://www.sidingmaster.com

Comment by Greg

Just stumbled on this and thought I recognised the clay product above. Looks similar to:

http://www.facade.co.nz/products/moeding-clay-tile-ventilated-facade-systems/

or:

http://www.australbricks.co.nz/nz/product_1897_terraade.php

Comment by Griff

[…] Posts Re-thinking Construction DocumentsSimple, modern furnitureRainscreensSun Screens InternationalSkylab, PortlandCor-ten Architectural SidingPhoenix Architecture: Part […]

Pingback by Modern House: materials and methods of the current time « BUILD Blog

[…] Construction DocumentsCor-ten Architectural SidingSimple, modern furnitureBoard & Batten SidingRainscreensSun Screens InternationalCasa Malaparte, CapriArchitecture and […]

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Is anyone familiar with companies that can provide the fixing systems for phenolic rainscreen panels?

Comment by Ken Ethridge, AIA, RIBA

Hello all, Great to hear and see your phenolic rain screen system ideas. My Based in NY has been fabricating and supplying Formica brand solid compact phenolic rain screen systems for quite awile We are the exclusive partner of Formica Europe and formica USA to bring this exciding product to the north american market. please fell free to call me and I will send you a complete sample pack via fed x. keep up the good work….Chris delgrosso
Jhc INC
718-649-1661
chrisdelgrosso@msn.com

Comment by chris delgrosso

[…]  We are using a rainscreen system.  Build Blog had a great post about them some time ago – click here to learn more about […]

Pingback by SIPs House Portland » Blog Archive » Waterproofing

[…] A vented rainscreen is basically an air gap in between the cladding and the water resistive barrier (WRB) applied to the sheathing of a house. It is vented at the top and bottom of the cladding on the home. This vented gap, allows any water that penetrates the cladding to freely drain down the WRB and away from the house. It also allows extra circulation during the summer months that helps to keep the house naturally cooler. For the best explanation and step by step detailing on vented rainscreens, check out this post on the BUILD blog. […]

Pingback by Home Slicker Instant Rainscreen House Wrap | 100K House Blog

We have been designing exteriors with Cembonit rainscreens on our last few projects here in central Canada. A common design issue is the cap flashing. We want minimal, ideal nothing. What have you found works best and how much venting are you leaving at the top? The Medina Residence looks to have no cap flashing ???

Comment by Todd

Todd – the cap flashing can actually be a fussy detail. You want something there to keep the sun off the membrane and debris out of the cavity of course. At the same time there is usually venting at the top of the wall and ideally the flashing is brought down further to protect the vent opening. The Medina residence does have flashing -it’s just a very small profile and is painted to match the panels. I’ll email you a couple of details we’ve been using. Stay tuned.

Comment by buildllc




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